Sump Flow Through Rate limitation on Skimmer Size?

[kenny b]

I'm trying to decide on the right skimmer for my new 110 gallon. The built-in overflow has an advertized maximum flow-rate of 700 gph and I'm wondering what would be about the maximum sized skimmer before diminishing return effects kick in? Surely for very large skimmers, dirty water would be skimmed so rapidly once it enters the sump that overly large skimmers is just wasting energy and space in the sump recirculating water that can't really be skimmed anymore. I'm aiming for about 70% acropora, 10% other SPS, 10% LPS, and 10% NPS. The skimmers I've been looking at thus far are the Aquamaxx EM 300, Aquamaxx EM 500, Eshopps Snow cone 300, and the Reef Octopus Diablo XS200 and Reef Octopus Diablo XS250.

Thanks!

[kenny b]

In other words, does a $600 skimmer really add anything more than a $300 or $400 one in this case? Does it really allow for a few more fish, or NPS corals in the tank?

[ca1ore]

No causality between skimmer performance and sump flow through. Some will tell you the two should be matched, but it's fuzzy logic at best. Frankly, the success of recirculating skimmers quickly puts any arguments on needing to match flow to rest. As long as you keep flow through the sump at 2x tank volume per hour or higher, to ensure adequate surface skimming and uniform heating, you will be fine.

The other thing to consider is that studies have suggested that even the most modern skimmers will only remove about 30% of the DOC. How 'big' a skimmer needs to be to remove all of this in a single pass is unclear, but, again, the existence of recirculating skimmers at least implies that multiple passes are required. My own personal rule-of-thumb is to use a skimmer rated for double my tank size at the median stocking level.